Molecular structure models of amorphous bismuth and cerium carboxylate catalyst precursors

Jincan Jin, Rebekah Habeger, Todd Yoder, David Coulliette, Andrew Eisenhart, Thomas Beck, Udari S. Kodithuwakku, Doo Young Kim, Chris Benmore, Rob Hart, Wilson D. Shafer

Research output: Contribution to journalArticlepeer-review

Abstract

As our societal need for materials and energy has grown, so has our need for catalyst processes in hydrogen production. A major function in these applications, for both homogenous and heterogeneous catalysis processes, is the synthesis of an active metal catalyst. It must first be soluble to control the physical properties of the metal being used. Recent work in metal precursors has begun to turn toward these metal carboxylate types of material. Structural models are proposed for bismuth 2-ethylhexanoate and 2,2-dimethyloctanoate and cerium 2-ethylhexanoate. The bismuth compounds have been characterized at different ratios of bismuth to carboxylate as solutions of the free acids. Their structures are most consistent with a Bi4(RCO2)12 motif where the Bi ions are arranged in a flattened tetrahedron with Bi – Bi distances of about 4.3 Å. There is evidence for Bi – O – Bi linkages at low free acid concentrations. The cerium compound is most consistent with a linear tetracerium molecule where the Ce – Ce distances repeat at about 4.3 Å out to 16.4 Å. The models were generated by analogy with known crystal structures and compared to high-energy x-ray scattering data. To further evaluate the models, DFT calculations were made, and the equilibrium geometries were compared. The vibrational spectra calculated from those geometries are presented and compared to the experimental results. Magnetization vs. temperature data was collected on the cerium compound, and its behavior was consistent with the proposed model. A geometrical approach to determining the dimensionality and relative positions of the metal ions in these structures is presented.

Original languageEnglish
Pages (from-to)350-357
Number of pages8
JournalCatalysis Today
Volume402
DOIs
StatePublished - Sep 15 2022

Bibliographical note

Funding Information:
The authors would like to thank the directors of The Shepherd Chemical Company for their support and for permission to publish this work. Mr. John Stueve, P.E. collected the Raman data on the bismuth samples. Drs. Denis Pelekhov and Camelia Selcu of The Ohio State University NanoSystems Laboratory collected the SQUID data and assisted the authors with workup and discussion. Professor Paul Martin supported T. Yoder during part of this work. Argonne National Lab is funded by United States Department of Energy under contract DE-AC02-06CH11357.

Funding Information:
The authors would like to thank the directors of The Shepherd Chemical Company for their support and for permission to publish this work. Mr. John Stueve, P.E., collected the Raman data on the bismuth samples. Drs. Denis Pelekhov and Camelia Selcu of The Ohio State University NanoSystems Laboratory collected the SQUID data and assisted the authors with workup and discussion. Professor Paul Martin supported T. Yoder during part of this work. Argonne National Lab is funded by United States Department of Energy under contract DE-AC02-06CH11357 .

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • Bismuth
  • Carboxylate
  • Catalytic precursor
  • Cerium carboxylate
  • Computational chemistry
  • Geometric conformation
  • SQUID magnetometry
  • Vibrational spectroscopy

ASJC Scopus subject areas

  • Catalysis
  • Chemistry (all)

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